This is a Continuation application of patent application Ser. No. 10/696,336, now U.S. Pat. No. 6,940,012 “METHOD AND APPARATUS FOR PROVIDING AN ENVIRONMENTAL BARRIER BETWEEN AN INTERIOR AND EXTERIOR OF AN ELECTRICAL ENCLOSURE USING A PLUG AND SEAL”, filed Oct. 28, 2003.
1. Field of the Invention
This invention relates to electrical enclosures, and more particularly to electrical enclosures having knockouts.
2. Description of the Related Art
Outdoor lighting systems are frequently used to provide spotlight and area lighting in locations that are exposed to moisture and particulate contaminants. Electrical enclosures are used in such environments to protect electrical components or electrical junctions used in the lighting systems from damage. One or more knockouts are provided in such enclosures to allow selective introduction of wiring into the interior while maintaining an environmental seal between exterior and interior portions of the electrical enclosure at both utilized and non-utilized knockouts.
Cost and convenience are important design considerations for a knockout. Typically, the knockout is threaded to accept a threaded cap during manufacture, with the cap removed by the user upon assembly of the lighting system. Such a configuration enables conduit or other threaded piping to be attached with a seal at the knockout location while protecting the interior of the electrical enclosure from moisture and contaminants. Unfortunately, use of the knockout is inconvenient because of the need to unscrew the cap.
Or, the knockout can be non-threaded, with its exterior circumference thinned to enable mechanical removal of the desired section such as by striking with a screwdriver or other solid object. A coupling is then added to the enclosure at the knockout to enable a conduit or other threaded piping to be attached with a seal. One example of this configuration includes an electrical enclosure offered by Hubbell Electrical Products, a Division of Hubbell Incorporated (Delaware) (part number 5320-0). The enclosure has a single knockout for introduction of wiring into the enclosure's interior. As is typical for this configuration, the knockout does not provide for a threaded portion to accept a conduit or other pipe thread connections for connection to the electrical enclosure. An additional fitting must be added, with a seal, to couple the conduit or other pipe thread connection to the knockout. Unfortunately, the additional coupling and time required to install the coupling adds to the cost of electrical system installation and is inconvenient for the user.
In either configuration, if multiple knockouts are provided, the non-utilized knockouts remain covered to maintain an environmental seal between exterior and interior portions of the electrical enclosure.
A need exists for an electrical enclosure that provides for selective introduction of wiring into its interior while maintaining an environmental barrier and without adding the expense and inconvenience of removing a threaded cap or adding a coupling prior to assembly.